Faculty Collaboration Database

Time-dependent effects of dim light at night on re-entrainment and masking of hamster activity rhythms. J Biol Rhythms 2010 Apr;25(2):103-12

Date

03/30/2010

Pubmed ID

20348461

DOI

10.1177/0748730409360890

Scopus ID

2-s2.0-77950240644 (requires institutional sign-in at Scopus site)   18 Citations

Abstract

Bright light has been established as the most ubiquitous environmental cue that entrains circadian timing systems under natural conditions. Light equivalent in intensity to moonlight (<1 lux), however, also strongly modulates circadian function in a number of entrainment paradigms. For example, compared to completely dark nights, dim nighttime illumination accelerated re-entrainment of hamster activity rhythms to 4-hour phase advances and delays of an otherwise standard laboratory photocycle. The purpose of this study was to determine if a sensitive period existed in the night during which dim illumination had a robust influence on speed of re-entrainment. Male Siberian hamsters were either exposed to dim light throughout the night, for half of the night, or not at all. Compared to dark nights, dim illumination throughout the entire night decreased by 29% the time for the midpoint of the active phase to re-entrain to a 4-hour phase advance and by 26% for a 4-hour delay. Acceleration of advances and delays were also achieved with 5 hours of dim light per night, but effects depended on whether dim light was present in the first half, second half, or first and last quarters of the night. Both during phase shifting and steady-state entrainment, partially lit nights also produced strong positive and negative masking effects, as well as entrainment aftereffects in constant darkness. Thus, even in the presence of a strong zeitgeber, light that might be encountered under a natural nighttime sky potently modulates the circadian timing system of hamsters.

Author List

Frank DW, Evans JA, Gorman MR

Author

Jennifer A. Evans PhD Assistant Professor in the Biomedical Sciences department at Marquette University

MESH terms used to index this publication - Major topics in bold

Animals
Behavior, Animal
Biological Clocks
Circadian Rhythm
Cricetinae
Cricetulus
Darkness
Light
Male
Phodopus
Photic Stimulation
Photoperiod
Physical Conditioning, Animal
Suprachiasmatic Nucleus
Time Factors